Vacuum switching chambers are known from the prior art which are forcibly cooled so as to increase the current-carrying capacity. The vacuum switching chamber is arranged in an insulating tube, through which air flows with the aid of a blower, with the result that, even in the event of a high current load, excessive heating of the vacuum switching chamber is avoided.
One problem with such an arrangement is the fact that the blower is active, i.e. needs to be driven. It requires maintenance and may fail.
The blower may possibly have a redundant design, as a result of which a higher degree of reliability can be achieved. Nevertheless, a higher degree of reliability of the cooling is desirable.
Furthermore, DE 39 41 388 A1 has disclosed a vacuum switching chamber which uses a heat pipe having cooling means for dissipating heat from the contact pieces, which heat pipe is coupled to the stationary upper contact piece and functions on the basis of the principle of the force of gravity. In this case, the lower contact piece, which is formed without a heat pipe, is connected movably to the housing via a folding bellows.
U.S. Pat. No. 4,005,297 has disclosed a vacuum switching chamber, in which the heat which arises is output via a heat pipe to cooling fingers, which are arranged radially around the heat pipe. Furthermore, it is also possible to use the heat pipe both in the moving contact piece and in the non-moving contact piece irrespective of the orientation with respect to the force of gravity, owing to the use of a condensation-assisting wick.
EP 1 002 758 A2 has described a vacuum switching chamber, in which an axial hole for accommodating a heat pipe is provided in the upper lifting ladder, which can be moved by a folding bellows. The total mass of the heat pipe is moved along when the contact piece is moved.